Individuals just need to play the in-game community events to take part.

Ah... I'm relieved! It means I can play the in-game community events, just like a time-trial. Because of that registration, I misunderstood and thought it was necessary to register to have a chance to enter the events. So I'll be able to do the events, as an individual, and finally get the last achievement (to play 20 community events) of this great game! I'm feeling happy